Due to their location in relatively unprotected sites, wind turbines often experience considerable exposure to environmental conditions during the turbine lifetime. Such exposure can often result in localised wearing or erosion of sections of the surfaces of the wind turbine blades, in particular along the blade leading edge. These eroded sections can result in fractures or cavities forming on the blade surface, which can impact upon the blade aerodynamic and noise performance, as well as upon the appearance of the blade. Accordingly, regular service inspection of blades in use can often reveal the need for localised blade surface repair operations.
Due to the considerable expense and difficulty involved in the demounting and subsequent transportation of blades installed on a wind turbine tower, such localised repair operations are often performed in the field, and in particular when the blade to be repaired is still mounted to the greater wind turbine structure. Such in-field repairs place substantial demands on the efficiency and ease-of-implementation of the repair procedure, to reduce the time and cost involved in carrying out the blade repair. Furthermore, as such repairs are carried out in the field, the difficulty in providing effective control of process variables such as air temperature, humidity levels, etc., can impact on the effectiveness of the repair performed. As a result, current blade repair solutions possess considerable limitations.
An example of a blade repair solution is the Alexit® BladeRep™ coating system, provided by Mankiewicz Gebr. & Co., which provides for two-component polyurethane-based repair coating which can be applied to a section of a blade to be repaired. Another example of a blade repair solution is the Wind Blade Protection Coating W4600 from 3M™. However, such systems have the limitation of a very narrow process window, reducing effectiveness in relatively difficult repair conditions, e.g. in relatively hot or cold climates, or environments with a relatively high humidity level.
Alternatives include UV-light-based curing systems, such as the RENUVO™ system provided by Gurit Holding AG., where a resin is applied which can be cured using a UV-light source. While such systems are generally not as sensitive to environmental conditions, such UV-based systems require the deployment of dedicated UV lamps for the curing process to work. In addition, UV-cured coatings often present reduced long-term performance as a cured coating, often requiring increased levels of maintenance and future repair operations when compared to polyurethane-based systems. Additionally, this type of material requires complicated and expensive packaging in order to protect it against UV light, which could thereby initiate the cure process prior to application.
It is an object of the invention to provide a wind turbine blade repair method and apparatus which provides improved performance over existing repair solutions.